The present invention relates to a fifth wheel hitch for receiving a kingpin of a trailer and one which has the ability to sense forces between the trailer bolster plate, kingpin and the fifth wheel and a circuit to process such sensed information.
The identification of forces between a truck trailer and a truck hitch is useful for a variety of reasons. Such information can be employed, for example, in an automatic braking system whereby signals from a sensing system can be employed to prevent excessive braking on one or more wheels or otherwise control braking for safe deceleration. In addition, such systems are helpful in alerting the vehicle operator to excessive trailer movement, such as pitching, yaw and/or potentially dangerous roll conditions.
As can be appreciated, the interconnection between a trailer kingpin and a fifth wheel assembly provides a relatively harsh environment for detection of the large forces involved and efforts to provide accurate sensing information with signals from a sensor which are linearly related to the detected forces has been difficult. U.S. Pat. Nos. 5,286,094 and 5,289,435 represent one sensor construction and a mounting employed for measuring push and pull forces on a hitch connection. It would be desirable, however, to provide additional information such as pitch, yaw and roll information for use by the driver in safely operating the vehicle.
The sensing of multiple axis force information between the coupling of a trailer to a tractor is difficult not only due to the harsh environment to which the equipment is exposed but also the relatively large and rapidly varying forces encountered and finally the difficulty in providing a linear output signal from sensors which may be employed.
The system of the present invention provides a sensing system which employs multiple sensors utilizing a mounting structure which can be integrated into a fifth wheel hitch and which is protected from the environment and capable of accurately measuring forces along longitudinal and vertical axes for providing information as to roll, pitch, and yaw. The system utilizes sensors which provide a relatively linear electrical output signal which can be used for displaying such forces, for generating alarms, or for controlling the vehicle operation.
Systems embodying the present invention comprise a fifth wheel having mounting boxes formed on an undersurface thereof on opposite sides of the kingpin receiving slot and a force-sensing unit mounted within each of said mounting boxes. Each force-sensing unit includes a forward and aft vertical sensor and a forward and aft longitudinal sensor. With a force-sensing unit on the left-side and the right-side of the fifth wheel assembly, eight such sensors provide signal information which can be used to determine roll, pitch and yaw movements derived from the detected vertical and longitudinal forces on the hitch.
In one embodiment of the invention, each of the sensors are mounted to the sensing unit utilizing elastomeric springs coupling the fifth wheel plate to the force-sensing unit and a plunger for coupling forces from said elastomeric spring to a force sensor itself. In this embodiment, the longitudinal sensors also include a pair of elastomeric springs for preloading the sensor such that it is capable of sensing forces in both directions. Also, in one embodiment of the invention, the plungers are mounted within a cylindrical aperture having a curved opening allowing the elastomeric spring to deform linearly into contact with the plunger as force is applied thereto.
With such a system, a force-sensing fifth wheel assembly is provided which measures forces in vertical and horizontal axes between the kingpin coupling to the fifth wheel and provides accurate signal information to an electrical circuit which can display pitch, roll and yaw and vertical load information to the vehicle for use in controlling the safe operation of the vehicle.
According to another embodiment of the present invention, a force-sensing unit for a fifth wheel assembly includes a housing, a first vertical sensor, a second vertical sensor, a first horizontal sensor and a second horizontal sensor. The housing is coupled to a fifth wheel between a tractor mountable bracket and a fifth wheel. The first vertical sensor is positioned in the housing forward of the lateral axis of the fifth wheel and the second vertical sensor is positioned in the housing rearward of the lateral axis of the fifth wheel. The first horizontal sensor is positioned in the housing forward of the lateral axis of the fifth wheel and the second horizontal sensor is positioned in the housing rearward of the lateral axis of the fifth wheel. In this manner, the force-sensing unit provides a total of four channels of force-sensing information, with each of the sensors being embedded within an elastomeric pad.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.